A bloke goes to his mate's fancy dress party with nothing but a naked girl on his back.

"What the hell are you supposed to be?" the host asks.

"I'm a snail," the bloke replies.

"What a load of crap!" the host spits. "How can you be a snail when all you've got is that naked girl on your back?"

"That's not a naked girl," the bloke replies. "That's Michelle."